Method and apparatus for face determination

ABSTRACT

Provided are a method and an apparatus for processing digital images, and more particularly, a method and an apparatus for face determination, wherein it is determined if a subject is a true subject based on distance information regarding a distance to the subject and face detection information. In an embodiment, the face detecting apparatus is a digital image processing apparatus and includes a digital signal processor for determining if a subject is a true subject based on distance information regarding a distance to the subject and face length information.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2009-0086667, filed on Sep. 14, 2009, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

Various embodiments of the invention relate to a method and an apparatusfor processing digital images, and more particularly, to a method and anapparatus for face determination, wherein it is determined whether asubject is a true subject or not based on distance information regardinga distance to the subject and face detection information.

General face detection techniques store characteristics of faces in adatabase and determine a face if characteristics of a face in live viewimages that are input in real time match the characteristics of faces inthe database. In this case, even when a non-face pattern includingsimilarities with the characteristics stored in the database is input asa live view image, the non-face pattern is detected as a face.

SUMMARY

Various embodiments of the invention provide a method and an apparatusfor face determination, wherein it is determined whether a subject is atrue subject or not based on distance information regarding a distanceto the subject and face detection information to reduce erroneous facedetections.

According to an embodiment of the invention, there is provided a facedetecting apparatus, which is a digital image processing apparatus,including a digital signal processor for determining whether a subjectis a true subject or not based on distance information regarding adistance to the subject and face length information.

The digital signal processor may include a focus adjusting unit foradjusting a focus of a live view image and calculating a distancebetween the subject and a lens; a face detection unit for detecting aface from the live view image with adjusted focus, calculating thelength of the detected face, and calculating an actual length of thedetected face based on a distance between the subject and the lens, thecalculated length of the face, and a focusing distance; and a controlunit for determining whether the subject is a true subject or not bycomparing the calculated actual length of the face and a pre-stored facelength reference value.

The face detecting apparatus may further include a storage unit forstoring at least one of each of face detection information, a minimumface length reference value based on experiments, and a maximum facelength reference value.

The face detecting apparatus may further include an informing unit foroutputting an informing signal indicating that the subject is not a truesubject in the case where it is determined that the subject is not atrue subject based on the comparison.

The informing signal may be either a pop-up message or a voice message.

According to another embodiment of the invention, there is provided aface detecting apparatus, which is a digital image processing apparatus,including a digital signal processor for determining whether a subjectis a true subject or not by comparing based on distance informationregarding a distance to the subject and face size information todistance information regarding a distance to the subject and face sizeinformation stored in a database.

The digital signal processor may include a storage unit for storing atleast one of each of face detection information and informationregarding face sizes according to the distances; a focus adjusting unitfor adjusting a focus of a live view image and calculating a distancebetween a subject and a lens; a face detection unit for calculating thesize of a face from the live view image with adjusted focus; and acontrol unit for determining that the detected face corresponds to atrue subject, in the case where face sizes according to the distances,the face sizes stored in the database are similar to the calculated facesizes according to the distances.

The face detecting apparatus may further include an informing unit foroutputting an informing signal indicating that the subject is not a truesubject in the case where it is determined that the subject is not atrue subject based on the comparison.

The informing signal may be either a pop-up message or a voice message.

According to another embodiment of the invention, there is provided amethod of operating a digital image processing apparatus, the methodincluding steps of (a) calculating information regarding a distance to asubject and face length information; and (b) determining whether thesubject is a true subject or not by using the calculated information.

The step (a) may include steps of (a-1) calculating a distance from thesubject to a lens; (a-2) detecting a face from a live view image andcalculating the length of the detected face; and (a-3) calculating anactual face length by using the distance from the subject to the lens,the calculated face length, and a focusing distance.

The step (b) may include steps of (b-1) comparing the calculated actualface size and pre-stored minimum/maximum face length reference values;and (b-2) determining whether the subject is a true subject or not basedon a result of the comparison.

The method may further include a step of outputting an informing signalto inform that the subject is not a true subject in the case where it isdetermined that the subject is not a true subject.

The informing signal may be either a pop-up message or a voice message.

According to another embodiment of the invention, there is provided amethod of operating a digital image processing apparatus, the methodincluding steps of (a) calculating information regarding a distance to asubject and face size information; and (b) determining whether thesubject is a true subject or not by comparing the obtained informationto pre-stored information regarding face sizes according to distances.

The step (a) may include steps of (a-1) adjusting a focus of a live-viewimage and calculating a distance from the subject to a lens; and (a-2)calculating the size of a face from the live view image with adjustedfocus.

In the step (b), it may be determined that the detected face correspondsto a true subject in the case where a stored face size according to adistance and the calculated face size according to the distance aresimilar to each other, and it may be determined that the detected faceis not a true subject in the case where face sizes according to thedistances, the face sizes stored in the database are not similar to thecalculated face sizes according to the distances.

The method may further include a step of outputting an informing signalto inform that the subject is not a true subject in the case where it isdetermined that the subject is not a true subject.

The informing signal may be either a pop-up message or a voice message.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of various embodiments ofthe invention will become more apparent by describing in detailexemplary embodiments thereof with reference to the attached drawings inwhich:

FIG. 1 is a block diagram of a face detecting apparatus according to anembodiment of the invention;

FIG. 2 is a block diagram showing the digital signal processor of FIG. 1in closer detail;

FIG. 3 is a pictorial diagram for describing face length calculationbase on face detection in FIG. 2;

FIG. 4 is a pictorial diagram for describing calculation of actual facelength of a subject in FIG. 2;

FIG. 5 is a pictorial diagram for describing determination that a faceis not a true face, based on the calculation of the actual face lengthof a subject in FIG. 2;

FIG. 6 is a pictorial diagram for describing determination that a facecorresponds to a true face, based on the calculation of the actual facelength of a subject in FIG. 2;

FIG. 7 is a pictorial diagram for describing detection of feature pointsof a face detected in FIG. 2 and obtainment of distance informationregarding the detected face;

FIG. 8 is a flowchart of a method for face determination by usingdistance information according to an embodiment of the invention; and

FIG. 9 is a flowchart of a method for face determination by usingdistance information according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a block diagram of a face detecting apparatus according to anembodiment of the invention. More specifically, FIG. 1 roughlyillustrates a digital photographing apparatus capable of detectingfaces, and hereinafter, the face detecting apparatus will be referred toas a digital photographing apparatus. However, embodiments of theinvention are not limited to the digital photographing apparatus shownin FIG. 1. The embodiments of the invention described below andmodifications thereof may also be applied to image processingapparatuses including, but not limited to, personal digital assistants(PDAs) and personal multimedia players (PMPs).

A central processing unit (CPU) 100 controls the overall operations of adigital image processing apparatus. Furthermore, the digital imageprocessing apparatus includes an operating console 200, which includeskeys via which a user generates electric signals. An electric signalfrom the operating console 200 is transmitted to the CPU 100, so thatthe CPU 100 may control the digital image processing apparatus accordingto the electric signal.

In the case of an image capturing mode, as an electric signal from auser is applied to the CPU 100, the CPU 100 analyzes the electric signaland controls a lens driving unit 11, an iris driving unit 21, and animaging device control unit 31, and thus the positions of a lens 10, anaperture of an iris 20, and the sensitivity of an imaging device 30 arecontrolled, respectively. The imaging device 30 generates data fromlight incident thereto, and an analog-to-digital converter (ADC) 40converts analog data output by the imaging device 30 into digital data.Here, the ADC 40 may be omitted based on characteristics of the imagingdevice 30.

Data from the imaging device 30 may be input to a digital signalprocessor (DSP) 50 via a memory 60, may be directly input to the DSP 50,or, if required, may be input to the CPU 100. Here, the memory 60includes a read-only memory (ROM) or a random access memory (RAM). Ifrequired, the DSP 50 may perform image processes, such as gammacorrection and white balance adjustment, on data from the imaging device30. Furthermore, as shown in FIG. 2, the DSP 50 may include a storageunit 51, a focus adjusting unit 52, a resizing unit 53, a face detectionunit 54, a control unit 55, and an informing unit 56. Here, variousmodifications may be made regarding the components; e.g., the storageunit 51, the focus adjusting unit 52, the resizing unit 53, the facedetection unit 54, the control unit 55, and the informing unit 56 may becomponents separate from the DSP 50. The operations of the componentsabove will be described below.

An image from data output by the DSP 50 is transmitted to a displaycontrol unit 81 either via the memory 60 or directly. The displaycontrol unit 81 controls a display unit 80 to display the image on thedisplay unit 80. Here, the display unit 80 may be a touch-screen.Furthermore, data output by the DSP 50 is input to a write/read controlunit 71 either via the memory 60 or directly, and the write/read controlunit 71 stores image data in a storage medium 70 either in response to asignal from a user or automatically. Alternatively, the write/readcontrol unit 71 may read data from an image file stored in the storagemedium 70 and input the data to the display unit 81 either via thememory 60 or via another route, so that an image is displayed on thedisplay unit 80. The storage medium 70 may either be detachably attachedor be permanently attached to a digital image processing unit.

Hereinafter, functions of the DSP 50 will be described with reference toFIG. 2. Two embodiments of the DSP 50 are described below, wherein inthe first embodiment, the DSP 50 determines whether a subject is a truesubject or not based on distance information regarding a distance to thesubject and face length information, and in the second embodiment, theDSP 50 determines whether a subject is a true subject or not based ondistance information regarding a distance to the subject and informationregarding the size of a face. The first embodiment will be describedwith reference to FIGS. 2 through 6, and the second embodiment will bedescribed with reference to FIGS. 2, 3, and 8.

First, the operations of the DSP 50 according to the first embodimentwill be described.

To determine whether a subject is a true subject or not based ondistance information regarding a distance to the subject and face lengthinformation, the DSP 50 includes the storage unit 51, the focusadjusting unit 52, the resizing unit 53, the face detection unit 54, thecontrol unit 55 and the informing unit 56.

The storage unit 51 stores at least one of face detection information, aminimum face length reference value (e.g., 250 mm) based on experiments,and a maximum face length reference value (e.g., 400 mm). Various sizesof detected faces are stored in the storage unit 51. For example, thesmallest size of a detected face stored therein is 14×14, and facedetection fails if the size of a detected face is smaller than thesmallest size.

The focus adjusting unit 52 adjusts a focus of a live view image andcalculates a distance D between a subject and the lens 10. The focusadjusting unit 52 moves a focus lens (not shown) in a focus adjustmentdirection according to a first shutter-release button input signal andadjusts a focus by detecting an in-focus position based on a subjectimage formed on the imaging surface of the imaging device 30 via thelens 10. Here, the focus adjusting unit 52 calculates the distance Dbetween a subject and the lens 10, and, when the first shutter-releasesignal is input, a light emitting unit (not shown) of a digitalphotographing apparatus emits infrared light onto a subject by using aninfrared light emitting diode (not shown), and a light receiving unit(not shown) receives infrared light, which is emitted by the lightemitting unit and reflected by the subject, and a signal correspondingto the light reception and measures the distance D.

A live-view image displayed on the display unit 80 has a resolution of960×240, for example, is updated every 33 ms, and is displayed on thedisplay unit 80.

In an embodiment, the resizing unit 53 reduces the resolution of alive-view image; e.g., a live-view image having a resolution of 960×240may be changed to an image having a resolution of 320×240.

The face detection unit 54 detects a face from a resized image, andcalculates a face detection starting point (x, y), and the width and thelength H (referred hereinafter as face length H_(image)) of the face.According to the feature-based face detecting method, the face detectionunit 54 detects constant facial features (face parts such as the eyes,nose, and mouth, skin texture, and skin tone) and calculates coordinatesof facial feature points. From among various facial features, skin toneis the most frequently used feature, because skin tone is less sensitivewith respect to movement, rotation, and changes in a size of a face.Furthermore, according to a template-based face detecting method, theface detection unit 54 creates a plurality of standard patternsregarding faces, and stores the patterns for face detection. Then, thepatterns are compared to an image one-by-one within a face browsingwindow to detect a face. A currently popular face detecting method is asupport vector machine (SVM)-based face detecting method. According tothe SVM-based face detecting method, a learning apparatus learns facesand non-faces by sub-sampling different regions of an image and detectsa face from an input image. The face information detections of the facedetection unit 54 are well-known in the art, and thus detaileddescriptions thereof will be omitted.

According to the first embodiment, as shown in FIG. 4, the facedetection unit 54 calculates the actual length H_(real) of a subject byusing the distance D from the subject to the lens 10, the calculatedface length H_(image), and a focusing distance f that are calculated bythe focus adjusting unit 52.

Actual Face Length (H _(real))=Face Length (H_(image))×D/f  [Mathematical Expression 1]

As shown in FIG. 4, the calculation of the actual face length H_(real)may be performed by either the face detection unit 54 or the controlunit 55.

The control unit 55 determines whether a subject is a true subject ornot by comparing the calculated actual face length H_(real) and facelength reference values (a minimum face length reference value (e.g.,250 mm) and a maximum face length reference value (e.g., 400 mm)) storedin the storage unit 51.

As shown in FIG. 5, when the distance D between a subject and the lens10 is 50 cm, the detected face length H_(image) is 20 mm, and thefocusing distance f is 50 mm, the calculated actual face length H_(real)is 200 mm according to Mathematical Expression 1. Since the calculatedactual face length H_(real), which is 200 mm, is smaller than theminimum face length reference value (e.g., 250 mm) stored in the storageunit 51, the control unit 55 determines that the subject of a displayedimage is not a true subject.

In the case where the subject of a displayed image is not a truesubject, the control unit 55 outputs a control signal for the informingunit 56 to output an alarm message. According to a control of thecontrol unit 55, the informing unit 56 outputs a message indicating thatthe subject of the displayed image is not a true subject, wherein themessage may be a pop-up message, a voice message, or other text or soundindicator.

As shown in FIG. 6, when the distance D between a subject and the lens10 is 1.0 m, the detected face length H_(image) is 20 mm, the focusingdistance f is 70 mm, and the calculated actual face length H_(real) is285 mm according to Mathematical Expression 1. Since the calculatedactual face length H_(real), which is 285 mm, is between the minimumface length reference value (e.g., 250 mm) and the maximum face lengthreference value (e.g., 400 mm) stored in the storage unit 51, thecontrol unit 55 determines that the subject of a displayed image is atrue subject. Then, an image may be captured in response to a secondshutter-release button input.

Next, the operations of the DSP 50 according to the second embodimentwill be described.

To determine whether a subject is a true subject or not by comparingdistance information regarding a distance to the subject and face sizeinformation to pre-stored information regarding face sizes according todistances, the DSP 50 includes the storage unit 51, the focus adjustingunit 52, the resizing unit 53, the face detection unit 54, the controlunit 55, and the informing unit 56.

The storage unit 51 stores at least one of face detection informationand information regarding face sizes according to the distances D from asubject to the lens 10. Various sizes of detected faces are stored inthe storage unit 51. For example, the smallest size of detected facestored therein is 14×14, and face detection fails if the size of adetected face is smaller than the smallest size. Furthermore, a size ofdetected face, in the case where the distance D from a subject to thelens 10 is 30 cm, stored therein is 20×20, for example.

The focus adjusting unit 52 adjusts a focus of a live view image andcalculates a distance D between a subject and the lens 10. A detaileddescription thereof is given above.

The resizing unit 53 reduces the resolution of a live-view imagedisplayed on the display unit 80; e.g., a live-view image having aresolution of 960×240 may be changed to an image having a resolution of320×240.

The face detection unit 54 detects a face from a resized image, andcalculates a face detection starting point (x, y), and the width and thelength H (referred hereinafter as face length H_(image)) of the face,and then a face size (face width×face length H) is calculated. In anembodiment, the face size calculation may be performed by either theface detection unit 54 or the control unit 55.

The control unit 55 determines whether a subject is a true subject ornot by comparing the calculated face size according to the distance Dfrom a subject to the lens 10 and information regarding face sizesaccording to the distances D from a subject to the lens 10, theinformation stored in the storage unit 51. As shown in FIG. 7, when thedistance D between a subject and the lens 10 is 30 cm, the detected facesize is 19×19, and a face size detected in the case where the distance Dfrom a subject to the lens 10 is 30 cm is 20×20 according to informationstored in the storage unit 51, for example, the two face sizes aresimilar to each other, and thus the control unit 55 determines that thesubject of a display image is a true subject. However, in the case wherea calculated face size according to the distance D from a subject to thelens 10 and face sizes according to the distances D from a subject tothe lens 10 according to information stored in the storage unit 51 arenot similar to each other, the control unit 55 determines that thesubject of a displayed image is not a true subject, and transmits acontrol signal to the informing unit 56 to output an alarm message. Inan embodiment, the size of a detected face is determined to be similarto or correspond to a face size stored in the imaging apparatus if thesize of the detected face is within a predetermined range of or equal tothe face size stored in the imaging apparatus. According to a control ofthe control unit 55, the informing unit 56 outputs a message indicatingthat the subject of the displayed image is not a true subject, whereinthe message may be a pop-up message or a voice message.

As described above, erroneous face detecting may be avoided bydetermining whether a subject is a true subject or not based on distanceinformation regarding a distance to the subject and face detectioninformation.

Hereinafter, a method of detecting a face according to an embodiment ofthe invention will be described in detail with reference to FIGS. 8 and9. The method of detecting a face according to the embodiment of theinvention may be performed in the digital image processing apparatus asshown in FIG. 1, wherein, in other embodiments, the main algorithm ofthe method may be performed in the DSP 50 by using peripheral componentsin the digital image processing apparatus.

First, referring to FIG. 8, the method of detecting a face according toan embodiment of the invention will be described.

For face detection, the DSP 50 establishes a database (not shown) andstores in the database at least one of each of face detectioninformation, a minimum face length reference value (e.g., 250 mm) basedon experiments, and a maximum face length reference value (e.g., 400mm). Various sizes of detected faces are stored therein. For example,the smallest size of a detected face stored therein is 14×14, and facedetection fails if the size of a detected face is smaller than thesmallest size. In an embodiment, the foregoing data may be stored in adata structure other than a database.

When a user turns on a digital image processing apparatus, the DSP 50displays a live view image on the display unit 80 (operation 801). Alive-view image displayed on the display unit 80 has a resolution of960×240, for example. Also, in an embodiment, the live-view image isupdated every 33 ms while being displayed on the display unit 80.

When a first shutter-release button is input (operation 803), the DSP 50automatically adjusts a focus of the displayed image (operation 805).The DSP 50 adjusts a focus of a live view image and calculates adistance D between a subject and the lens 10. Detailed descriptionsregarding the focus adjustment and the calculation of the distance Dbetween a subject and the lens 10 are given above.

After the focus adjustment and the calculation of the distance D betweena subject and the lens 10 are completed, the DSP 50 detects a face froma live view image with adjusted focus (operation 807).

The DSP 50 reduces the resolution of a live-view image for facedetection; e.g., a live-view image having a resolution of 960×240 may bechanged to an image having a resolution of 320×240. Next, DSP 50 detectsa face from a resized image, and calculates a face detection startingpoint (x, y), and the width and the length H (referred hereinafter asface length H_(image)) of the face, as shown in FIG. 3. Next, as shownin FIG. 4, the DSP 50 calculates the actual length H_(real) of a subjectby using the distance D from the subject to the lens 10, the calculatedface length H_(image), and the focusing distance f that are calculatedby the focus adjusting unit 52 (operation 809), where the actual facelength H_(real) is calculated according to Mathematical Expression 1.

After the calculation of the actual face length H_(real), the DSP 50determines whether a subject is a true subject or not by comparing thecalculated actual face length H_(real) and face length reference values(a minimum face length reference value (e.g., 250 mm) and a maximum facelength reference value (e.g., 400 mm)) stored in the database(operations 811 and 813).

As shown in FIG. 5, since the calculated actual face length H_(real),which is 200 mm, is smaller than the minimum face length reference value(e.g., 250 mm) stored in the database, the control unit 55 determinesthat the subject of a displayed image is not a true subject, and outputsa message indicating that the subject of the displayed image is not atrue subject, wherein the message may be a pop-up message or a voicemessage (operation 815).

As shown in FIG. 6, since the calculated actual face length H_(real),which is 285 mm, is between the minimum face length reference value(e.g., 250 mm) and the maximum face length reference value (e.g., 400mm) stored in the database, the DSP 50 determines that the subject of adisplayed image is a true subject (operation 817). Then, an image may becaptured in response to a second shutter-release button input.

Next, referring to FIG. 9, a method of detecting a face according toanother embodiment of the invention will be described.

For face detection, the DSP 50 establishes a database (not shown) andstores in the database at least one of face detection information andinformation regarding face sizes according to the distances D from asubject to the lens 10. Various sizes of detected faces are stored inthe database. For example, the smallest size of a detected face storedtherein is 14×14, and in an embodiment, face detection fails if the sizeof a detected face is smaller than the smallest size. Furthermore, asize of a detected face, in the case where the distance D from a subjectto the lens 10 is 30 cm, stored therein is 20×20, for example.

When a user turns on a digital image processing apparatus, the DSP 50displays a live view image on the display unit 80 (operation 901). Alive-view image displayed on the display unit 80 has a resolution of960×240, for example. Also, the live-view image is updated every 33 mswhile being displayed on the display unit 80.

When a first shutter-release button is input (operation 903), the DSP 50automatically adjusts a focus of the displayed image (operation 905).The DSP 50 adjusts a focus of a live view image and calculates adistance D between a subject and the lens 10. Detailed descriptionsregarding the focus adjustment and the calculation of the distance Dbetween a subject and the lens 10 are given above.

After the focus adjustment and the calculation of the distance D betweena subject and the lens 10 are completed, the DSP 50 detects a face froma live view image with adjusted focus (operation 907). The DSP 50reduces the resolution of a live-view image for face detection; e.g., alive-view image having a resolution of 960×240 may be changed to animage having a resolution of 320×240. Next, the DSP 50 detects a facefrom a resized image, calculates a face detection starting point (x, y),and the width and the length H (referred hereinafter as face lengthH_(image)) of the face, as shown in FIG. 3, and then calculates a facesize (face width×face length H)

Next, the DSP 50 compares the calculated face size according to thedistance D from a subject to the lens 10 and information regarding facesizes according to the distances D from a subject to the lens 10 storedin the database, and then determines whether they are similar to eachother or not (operations 909 and 911).

As shown in FIG. 7, when the distance D between a subject and the lens10 is 30 cm and the detected face size is 19×19 and a face sizedetected, in the case where the distance D from a subject to the lens 10is 30 cm, is 20×20 according to information stored in the database, forexample, the two face sizes are similar to each other, and thus the DSP50 determines that the subject of a display image is a true subject(operation 913).

However, in the case where a calculated face size according to thedistance D from a subject to the lens 10 and face sizes according to thedistances D from a subject to the lens 10 according to informationstored in the database are not similar to each other, the DSP 50determines that the subject of a displayed image is not a true subject,and outputs a message indicating that the subject of the displayed imageis not a true subject, wherein the message may be a pop-up message or avoice message (operation 915).

As described above, according to embodiments of the invention, it isdetermined whether a subject is a true subject or not based on distanceinformation regarding a distance to the subject and face detectioninformation. Therefore, erroneous face detections may be reduced.

For the purposes of promoting an understanding of the principles of theinvention, reference has been made to the preferred embodimentsillustrated in the drawings, and specific language has been used todescribe these embodiments. However, no limitation of the scope of theinvention is intended by this specific language, and the inventionshould be construed to encompass all embodiments that would normallyoccur to one of ordinary skill in the art.

While various embodiments of the invention are described in terms offunctional block components, such functional blocks may be realized byany number of hardware and/or software components configured to performthe specified functions. For example, embodiments of the invention mayemploy various integrated circuit components, processing elements, logicelements, etc.

The particular implementations shown and described herein areillustrative examples of the invention and are not intended to otherwiselimit the scope of the invention in any way. The connecting lines, orconnectors shown in the various figures presented are intended torepresent exemplary functional relationships and/or physical or logicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships, physical connectionsor logical connections may be present in a practical device. Moreover,no item or component is essential to the practice of the inventionunless the element is specifically described as “essential” or“critical”.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural. Furthermore, recitation of ranges of values herein are merelyintended to serve as a shorthand method of referring individually toeach separate value falling within the range, unless otherwise indicatedherein, and each separate value is incorporated into the specificationas if it were individually recited herein. Finally, the steps of allmethods described herein can be performed in any suitable order unlessotherwise indicated herein or otherwise clearly contradicted by context.The use of any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, it will be understood bythose of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the invention as defined by the following claims.

What is claimed is:
 1. A face detecting apparatus for detecting a faceof a subject in an image comprising: a digital signal processor fordetermining if the subject is a true subject based on distanceinformation regarding a distance to the subject and face lengthinformation.
 2. The face detecting apparatus of claim 1, wherein thedigital signal processor comprises: a focus adjusting unit for adjustinga focus of a live view image and calculating a distance between thesubject and a lens; a face detection unit for detecting a face from thelive view image with adjusted focus, calculating a displayed face lengthof the detected face, and calculating an actual face length of thedetected face based on a distance between the subject and the lens, thecalculated displayed face length, and a focusing distance; and a controlunit for determining if the subject is a true subject by comparing thecalculated actual face length of the face and a pre-stored face lengthreference value.
 3. The face detecting apparatus of claim 2, furthercomprising a storage unit for storing at least one of face detectioninformation, a minimum face length reference value based on experiments,and a maximum face length reference value.
 4. The face detectingapparatus of claim 3, further comprising an informing unit foroutputting an informing signal indicating that the subject is not a truesubject if it is determined that the subject is not a true subject basedon the comparison.
 5. The face detecting apparatus of claim 4, whereinthe informing signal is one of a pop-up message and a voice message. 6.A face detecting apparatus for detecting a face of a subject in an imagecomprising: a digital signal processor for determining if the subject isa true subject by comparing distance information regarding a distance tothe subject and face size information regarding the subject topre-stored distance information and face size information.
 7. The facedetecting apparatus of claim 6, wherein the digital signal processorcomprises: a storage unit for storing at least one of face detectioninformation and information regarding face sizes according to thedistances; a focus adjusting unit for adjusting a focus of a live viewimage and calculating a distance between the subject and a lens; a facedetection unit for detecting a face in the live view image andcalculating the size of the face with adjusted focus; and a control unitfor determining if the detected face corresponds to a true subject bycomparing the calculated face size of the detected face to a pre-storedface size according to distance.
 8. The face detecting apparatus ofclaim 6, further comprising an informing unit for outputting aninforming signal indicating that the subject is not a true subject if itis determined that the subject is not a true subject based on thecomparison.
 9. The face detecting apparatus of claim 8, wherein theinforming signal is one of a pop-up message and a voice message.
 10. Amethod of operating a digital image processing apparatus, the methodcomprising steps of: (a) calculating information regarding a distance toa subject and face length information; and (b) determining if thesubject is a true subject by using the calculated information.
 11. Themethod of claim 10, wherein (a) comprises steps of: (a-1) calculating adistance from the subject to a lens; (a-2) detecting a face from a liveview image and calculating the length of the detected face; and (a-3)calculating an actual face length by using the distance from the subjectto the lens, the calculated face length, and a focusing distance. 12.The method of claim 11, wherein (b) comprises steps of: (b-1) comparingthe calculated actual face length and at least one of a pre-storedminimum face length reference value and a pre-stored maximum face lengthreference value; and (b-2) determining if the subject is a true subjectbased on the comparison.
 13. The method of claim 12, further comprisinga step of outputting an informing signal to inform that the subject isnot a true subject if it is determined that the subject is not a truesubject.
 14. The method of claim 13, wherein the informing signal is oneof a pop-up message and a voice message.
 15. A method of operating adigital image processing apparatus, the method comprising steps of: (a)calculating information regarding a distance to a subject and face sizeinformation; and (b) determining if the subject is a true subject bycomparing the calculated information to pre-stored information regardingface sizes according to distances.
 16. The method of claim 15, wherein(a) comprises steps of: (a-1) adjusting a focus of a live view image andcalculating a distance from the subject to a lens; and (a-2) calculatingthe size of a face from the live view image with adjusted focus.
 17. Themethod of claim 15, wherein, in the step (b), it is determined that thedetected face corresponds to a true subject if a stored face sizeaccording to a distance corresponds to the calculated face sizeaccording to the distance, and it is determined that the detected faceis not a true subject in the case where the calculated face size doesnot correspond to a face size stored in the database according to thedistance.
 18. The method of claim 17, further comprising a step ofoutputting an informing signal to inform that the subject is not a truesubject if it is determined that the subject is not a true subject. 19.The method of claim 18, wherein the informing signal is one of a pop-upmessage and a voice message.